1. Field of the Invention
The invention relates to a position indicating apparatus, more particularly to an apparatus that indicates position of an incident light beam and that is used in the calibration of light-emitting instruments.
2. Description of the Related Art
Light-emitting instruments are required to be calibrated before being sold to consumers. The light-emitting instrument generally includes a light emitter that generates a light beam, and a sighting unit that is provided with a cross hair. The cross hair includes a pair of lines that intersect at a reference point, and has a specified position relationship with the light emitter.
A conventional method for calibrating an optical axis of the light beam generated by the light emitter of the light-emitting instrument includes the steps of:
1. forming a reference mark, which includes a pair of lines that intersect at a reference point, and a target area, which has a reference position relationship with the reference mark, on a surface of a wall;
It is noted that the reference position relationship between the reference mark and the target area corresponds to the specified position relationship between the cross hair on the sighting unit and the light emitter.
2. with the light-emitting instrument disposed at a distance away from the surface of the wall, aligning the cross hair on the sighting unit of the light-emitting instrument with the reference mark on the surface of the wall; and
3. calibrating the optical axis of the light beam generated by the light emitter of the light-emitting instrument such that the light beam is incident upon desired position in the target area.
Although the aforementioned conventional method may be conducted to calibrate the optical axis of the light beam generated by the light emitter of the light-emitting instrument, since the light-emitting instrument is required to be located at a relatively far distance from the wall in order for the optical axis to be accurately calibrated, the position of the incident light beam in the target area may not be clearly visible to the tester who is operating the light-emitting instrument. As such, during the calibration, the tester has to walk back and forth between the wall and the light-emitting instrument to verify the position of the incident light beam in the target area and to calibrate the optical axis of the light beam, which is inconvenient, error prone, and time consuming. Otherwise, an assistant has to be positioned near the wall to assist the tester during the calibration operation, which results in an increase in labor costs.